1. Technical Field
The present invention relates to an engine air intake structure provided with a partition plate that divides an air intake passage of an engine.
2. Related Art
Like the engine disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 2014-101774, there has been developed a technique by which a partition plate that divides an air intake passage into two paths (first and second paths) is provided in order to generate a tumble (vertical vortex) flow in the intake air flowing into a cylinder. When there is a small amount of intake air flowing through the passage, the first path separated by the partition plate is closed by a tumble generation valve (TGV), thereby speeding up the intake air flowing into a combustion chamber through the second path to generate a tumble flow in the combustion chamber.
In addition, JP-A No. 2014-101774 discloses an example of a structure in which a stepped surface is provided on an inner wall of the first path. When the opening of the TGV is minimized, an end of a TGV valve opposes the stepped surface from the upstream side with a narrow clearance therebetween such that intake air leakage is reduced.
The TGV is operated by an electric motor or other actuator. To protect the actuator, a clearance is provided between the end of the valve and the inner wall surface so that the end of the valve does not come into contact with the inner wall surface when the TGV is placed in a closed position. To check whether such a clearance falls within a design range, a thickness gauge or the like is inserted.
However, if the stepped surface is provided on the inner wall surface of the first path, the clearance between the inner wall surface and the end of the valve is invisible when the first path is viewed from the downstream side, which makes it impossible to measure the clearance even by inserting the thickness gauge into the first path from the downstream side. For instance, if the thickness gauge cannot be inserted into the first path from the upstream side due to curved passage form, it is impossible to measure the clearance.